Effects of brinzolamide on rabbit ocular blood flow in vivo and ex vivo.

AIM: To investigate if significant improvement of optic disc blood flow (ODBF) occurs after instillation of brinzolamide onto rabbit eyes. METHODS: Testing of bilateral intraocular pressure (IOP) and left ODBF in 10 male rabbits took place every 3h over a 24h period. Brinzolamide (1% ophthalmic solution, two drops at 9:00 and 21:00) was administered to the left eye. ODBF, assessed using laser speckle flowgraphy, was determined as the mean blur rate (MBR). Furthermore, the effect of brinzolamide on isolated rabbit ciliary arteries using isometric tension recording system was performed. RESULTS: After brinzolamide instillation, IOP was significantly decreased in the left eye. MBR-vessel was greater at 18:00 and 21:00 (P<0.05) than in the controls. MBR-tissue and MBR-average were greater at 18:00 (P<0.05) than in the controls. For isolated arteries pre-contracted with a high-K solution, brinzolamide induced concentration-dependent relaxation, reaching 46.1%±9% (n=21) at 1 mmol/L. In Ca(2+)-free solutions, incubation with brinzolamide suppressed 1 µmol/L histamine-induced contractions (P<0.05). CONCLUSION: Brinzolamide decreases IOP and increases ocular blood flow. The direct vasodilatory effect of brizolamide is mediated by suppression of Ca(2+) release from intracellular calcium stores.